EFFECTS OF DAY LENGTH AND LIGHT QUALITY ON THE ULTRASTRUCTURE OF THE PALISADE PARENCHYMA CELLS OF POTATO PLANTS

Using electron microscopic morphometry, the chloroplast and mitochondr ion structures in palisade mesophyll cells were studied in leaves of p otato (Solanum andigenum Juz et Buk.) plants grown under a short or lo ng day under blue or red light. The cell surface area and the number o f chloroplasts and mitochondria per cell were most affected by light q uality: they increased in blue light and decreased in red light. Membr ane structure expression in the organelles (chloroplast grana and mito chondrion cristae) was dependent on the photoperiod duration. These di fferences were more pronounced with a long day and when the plants wer e grown in blue rather than in red light. It is concluded that the rep roductive development of the potato and membrane structural changes in the palisade cells of potato leaves are highly responsive to photoper iod duration and light quality. This fact may present indirect evidenc e for the involvement of the membrane structures in the leaf phase of the photoperiodic control of flowering.